The subject matter of the present invention relates generally to lumber positioning and feeding apparatus, and in particular to such apparatus used for feeding a lumber edger including an edging optimizer which determines a reference axis which may be the optimum yield axis of the lumber and aligns such reference axis with the cutting axis of the edger to optimize the yield of boards cut from lumber.
It has been previously proposed in U.S. Pat. No. 3,736,968 of Mason issued June 5, 1973 to provide an edging optimizer in which a reference axis corresponding to the optimum yield axis of a flat piece of lumber with uncut rough edges, sometimes referred to in the industry as a "cant" or a "flitch", is determined electronically by scanning the lumber with light beams. The scanner includes a plurality of light sources and associated light detectors or photocells mounted in aligned pairs at longitudinally spaced positions along the flitch with the outputs of the photocells being connected to a data processing unit such as a digital computer which calculates the optimum yield axis. The flitch is aligned by adjustable stops on the conveyor which are controlled by the computer, with its optimum yield axis aligned with the cutting axis of the edger. U.S. Pat. No. 3,970,128 of Kohlberg issued July 20, 1976 shows a similar teaching except the flitch is stopped during scanning. A somewhat similar lumber edger apparatus employing automatic scanning with a plurality of light sources is disclosed in U.S. Pat. No. 4,196,648 of Jones et al issued Apr. 8, 1980 which shows a computer program for operating a digital computer to determine a side edge reference axis and the location of the edger saw cuts relative to the reference axis on the lumber being scanned.
An improved scanner apparatus and method for measuring the width and locating the edge of an elongated object such as a lumber plank or flitch is shown in U.S. Pat. No. 4,097,159 of Strandberg issued June 27, 1978 which may be used as the scanner in the edging optimizer apparatus of the present invention.
In addition, U.S. Pat. No. 4,269,245 of Fornell et al issued May 26, 1981 shows an optimizing edger apparatus employing automatic light beam scanning and a computer to determine the reference axis of the lumber, and which uses a plurality of adjustable slides and clamps mounted only at the alignment position. Each clamp includes two pairs of adjustable clamp members which are mounted on opposite sides of the center line or cutting axis of the edger in order to clamp the lumber fed between such clamp members and to align its reference axis with such cutting axis in response control signals from the computer. However, in none of these prior apparatus is the lumber cant or flitch clamped by the clamp means at a location remote from the alignment position immediately after scanning and skewed until its reference axis is parallel to the cutting axis of the edger before it is transferred to the aligned position, in the manner of the present invention. In addition, unlike such prior apparatus the present clamp means is pivoted between an extended condition above the conveyor where it clamps the lumber and a retracted condition where it is below the conveyor so that such clamp means can return beneath the lumber from the aligned position to the clamping position.
As a result of these differences, the edging optimizer apparatus of the present invention has several advantages over the prior apparatus including a much faster operation which is capable of feeding up to 21 boards per minute into the edger, whereas the previous apparatus only fed a maximum of 14 boards per minute maximum. This faster operation greatly increases production of the saw mill. In addition, the lumber feeding apparatus employed in the present invention has a more trouble-free operation with less jamming because of the more positive feeding action produced by clamping the boards before they are transferred from the scanner to the aligned position. Furthermore, the present pivoted clamp apparatus is simpler and less subject to jamming because it does not require conveying means for feeding the boards over the top of one of the clamp members and down into an alignment position between the clamp members as in the prior clamp apparatus. This is avoided in the present apparatus by rotating the clamp members between the entended and retracted conditions so that they can pass beneath the lumber when retracted to return from the aligned position to the clamping position and then be pivoted to an extended condition to raise the clamp members above the lumber on opposite sides of the lumber prior to clamping.